Scavenge device for refrigerant compressor systems



May 6, 1969 D. c. DERRAGON, JR 3,442,439

SCAVENGE DEVICE FOR REFRIGERANT COMPRESSOR SYSTEMS Filed June 30, 1967 E V!) 0R9 TOR MOTOR IN VENTUR J y gf mz United States Patent 3,442,439 SCAVENGE DEVICE FOR REFRIGERANT COMPRESSOR SYSTEMS Don C. Derragou, Jr., Pembina, N. Dak., asslgnor to Motor Coach Industries Inc., Pembina, N. Dak. Filed June 30, 1967, Ser. No. 650,351 Int. Cl. F04b 49/02, 49/06; F25b 41/00 US. Cl. 230-24 ABSTRACT OF THE DISCLOSURE The invention relates to a refrigerant compressor that is driven during both the unloaded and loaded conditions and which includes a solenoid operated valve in a scavenging conduit which extends between the high pressure cavity of the compressor to the crankcase thereof, said valve being opened during the unloaded condition and closed during the loaded condition.

The invention relates to new and useful improvements in refrigeration compressors, particularly refrigeration compressors which are adapted to run continuously during both loaded and unloaded conditions.

With continuous operating, full unloading type airconditioning compressors and the like, the compressor runs continuously as long as the engine of the vehicle or the like is operating. These compressors are unloaded by various mechanisms and lifter pins which lift the suction or inlet valves to full open position therefore preventing the gas from being compressed during the time the compressor is unloaded in this manner.

During these conditions, a low velocity gas pressure will build up due to the speed of the pistons and the fact some compression exists due to the restriction of the exit parameters. The discharge valves will therefore open allowing a small quantity of gas to circulate.

Compression pressure at this time is, of course, reduced from normal operating pressure and therefore there is a tendency for the lubricating oil to by-pass the piston rings. This is reinforced by the inward movement of the pistons which allows a higher pressure to exist in the crankcase thereby forcing oil around the rings into the compression chambers.

Also in the unloaded condition, frictional heat is transmitted to the oil which, when reaching approximately 180 F. begins to vaporize and is carried through the discharge valves to the high pressure cavity of the compressor where it begins to condense. If this condition is continued for prolonged periods, all the lubricating oil can be carried out of the compressor sump or crankcase and will be deposited in discharge lines and in the core of the condenser. It cannot be returned to the compressor due to lack of velocity of gas to carry the oil, therefore, without lubrication, compressor bearings will be damaged. This lack of oil also results in damage to the compressor, inasmuch as the lubricating oil is also used to cool the compressor crankshaft seal, so this lack of oil has a tendency for premature failure of the seal. Furthermore, the oil pressure is also required to load the compressor to increase the velocity that carries the lubricating oil back from the system to the crankcase.

In the loaded condition, of course, the refrigerant gas is pumped through the system at a high velocity and returns to the compressor at loW pressure and hence low temperature thus controlling the operating temperature of the compressor lubricating oil. Throughout the loaded cycle, a small portion of lubricating oil is carried with the refrigerant gas to the condenser and evaporator coils and is returned to the compressor due to the velocity of 4 Claims 3,442,439 Patented May 6, 1969 the gas moving in the system, the term gas covering the refrigerant either in gas use or liquid form.

The provision of the scavenger system hereinafter to be described, prevents oil from being carried into the refrigeration system during the unloaded condition and thereby prevents the faults hereinabove enumerated.

With the foregoing in view, and such other objects, purposes or advantages as may become apparent from consideration of this disclosure and specification, the present invention consists of the inventive concept in whatsoever way the same may be embodied having regard to the particular exemplification or exemplifications of same herein, with due regard in this connection being had to the accompanying figures in which:

FIGURE 1 is a partially schematic and partially sectioned front elevation of a compressor showing the location of the invention schematically.

FIGURE 2 is a wiring schematic showing one method of automatically operating the device.

FIGURE 3 is an enlarged cross sectional view of the restrictor valve portion of the conduit.

FIGURE 4 is a vertical section through a typical compressor showing the location of the invention therein.

In the drawings like characters of reference indicate corresponding parts in the different figures.

Proceeding therefore to describe the invention in detail, reference should first be made to FIGURE 4 which shows a two cylinder compressor of typical design.

Briefly it consists of pistons 10 operating in cylinders 11 and connected to a common crankshaft 12 within a crankcase 13, carrying lubricating oil 14 in the usual way.

A cylinder head 15 extends over the two piston and cylinder assemblies and a barrier 16 between the cylinders defines a high pressure cavity 17 above the cylinder and piston assemblies.

A discharge valve outlet 18 connected to the high pressure cavity.

A suction gas passage 19 connects to the crankcase and communicates with the cylinders 11 above pistons 10 when the suction valves 20 are opened. Mechanical means 21 taking the form of valve lifter pins and springs, are provided to raise the suction valves clear of the seats during the unloaded condition of operation, this operation being conventional in design.

Discharge valves 22 are provided above the cylinders 11 and communicate between the cylinders and the high pressure cavity 17.

Briefly the operation is as follows. As the pistons 10 descend, an area of low pressure is formed above the pistons which is lower than the pressure within the crankcase so that the suction valves 21 open thus allowing vapour to flow into the cylinders above the pistons. As the piston rises, this vapour is compressed thus closing the suction valves. Compression continues until a pressure above the condensing pressure is reached at which time the discharge valves open thus permitting the compressed vapour to fiow into the high pressure cavity and thence outwardly of the discharge valve outlet.

There is normally a small quantity of oil situated within the high pressure cavity and the amount is controlled by the position of the scavenging conduit connection 23 Within the discharge cavity. The scavenged conduit 24 is connected to this outlet and extends to the crankcase, being connected therewith above the oil level 25, as indicated at 26. A scavenged solenoid valve 27 is situated within the scavenged conduit and is conventional in construction. A high-low pressure switch assembly 28 is also in circuit with the compressor and is conventional in construction.

It has been found convenient to connect the high line 29 of the switch 28 to a T union 30 to which the portion 24 of the scavenge line is connected immediately prior to connection to the solenoid valve 27. The portion 31 of the T union connects to conduit 29 and the portion 24 of the scavenge conduit connects to the portion 32 of the T union. The stem 33 of the T union then connects to the solenoid valve 27 and in this connection I have provided a restrictor 34 in this portion to protect the compressor seal (not illustrated) from high pressures in the event of scavenged solenoid malfunction during the loaded cycle. Also as this restrictor is smaller than the conventional compensating port (not illustrated) between the suction cavity and the crankcase, crankcase oil would not be lost back through the suction cavity even if the solenoid fails during the alerted condition although it will, of course, impair the total capacity of the compressor in regard to ton capacity.

FIGURE 2 shows one schematic operating diagram of the device and it will be appreciated that the compressor normally is running all the time the engine of the vehicle is running, it being understood that the compressor is mechanically driven by the engine of the vehicle.

When the operator requires air conditioning, he closes the main switch 35. This connects the battery 36 to the circuit and closes both the compressor solenoid 37 and the scavenged solenoid valve 27. The compressor solenoid completes the circuit with the compressor motor and commences operating the compressor in the loaded condition, the scavenged solenoid having closed off the scavenged line.

As long as the system is working within the set limitations, the high-low pressure switch 28 will be closed.

However, if the operating limits are exceeded, the switch 39 opens thus opening the solenoid 37 and cutting out the operation of the compressor. However, solenoid 27 remains closed under these conditions so that the device does not cycle.

When the operator no longer requires air conditioning, he opens the switch 35 thus opening both solenoids 37 and 27 thus placing the scavenged line in operation during the unloaded conditions of operation of the compressor.

Although the device is designed primarily for use within air conditioning systems in vehicles such as motor coaches and the like, nevertheless it will be appreciated that it will find use under varying conditions.

Various modifications can be made within the scope of the inventive concept disclosed. Accordingly, it is intended that what is described herein should be regarded as illustrative of such concept and not for the purpose of limiting protection to any particular embodiment thereof, but that only such limitations should be placed upon the scope of protection to which the inventor hereof is entitled, as justice dictates.

What is claimed to be the present invention is:

1. In a continuously driven reciprocating piston type refrigerant compressor having a low pressure side containing lubricating oil, a high pressure side, and valve means operative for delivering refrigerant from the low pressure side to the high pressure side when the compressor is loaded and also for holding refrigerant in the low pressure side when the compressor is unloaded, an improvement comprising oil scavenging means whereby lubricating oil passing from the low pressure side to the high pressure side through said valve means when the compressor is unloaded may be returned to the low pressure side, said scavenging means being separate and distinct from said valve means and comprising an oil scavenging conduit extending from the high pressure side to the low pressure side of the compressor, a scavenger valve provided in said conduit, said scavenger valve being normally closed when the compressor is loaded, and means responsive to unloading of the compressor for opening said scavenger valve.

2. The device as defined in claim 1 together with a restricted flow orifice provided in said conduit in series with said scavenger valve.

3. In a continuously driven refrigerant compressor including a cylinder with a .reciprocable piston, an oil containing crankcase constituting the low pressure side of the compressor, a compression chamber constituting the high pressure side of the compressor, outlet valve means communicating said cylinder with said compression chamber, and inlet valve means which are operative to admit refrigerant from said crankcase to said cylinder when the compressor is loaded and which are held open when the compressor is unloaded, an improvement comprising oil scavenging means whereby oil passing from said crankcase past said piston and through said outlet valve means into said compression chamber when the compressor is unloaded may be returned to the crankcase, said scavenging means being separate and distinct from both said valve means and comprising an oil scavenging conduit extending from said compression chamber to said crankcase, a scavenger valve provided in said conduit, said scavenger valve being normally closed when the compressor is loaded, and means responsive to unloading of the compressor for opening said scavenger valve.

4. The device as defined in claim 3 together with a restricted flow orifice provided in said conduit in series with said scavenger valve.

References Cited UNITED STATES PATENTS 912,866 2/1909 Massa 62-196 1,983,550 12/1934 Lee 62-196 2,039,089 4/1936 Koch 62-196 XR MEYER PERLIN, Primary Examiner.

US. Cl X.R. 

